The present invention is directed to a modular flotation support collar having a slidably adjustable pen divider, and to a method for construction thereof using interchangeable component parts. The method and component parts of the present invention are particularly suited for use in the construction of aquaculture fish pens.
Growing consumer awareness in recent years of the health benefits accruing from lower consumption of saturated fats and cholesterol in the diet has resulted in reduced consumption of red meats and increasing demand for seafoods, particularly fish. Traditional harvesting techniques, however, have been unable to meet this growing demand for seafood due in part to limited, and in many cases decreasing, supplies of fish, particularly the more popular species such as salmon. Efforts to economically satisfy this growing demand for seafood have turned to aquaculture thereby nourishing the expansion of the fish farming industry. Fish pens are also used by private organizations and state and federal agencies in fish enhancement programs directed to particular species.
Fish are typically grown in a system of moored or anchored fish pens. The pens are comprised of underwater net cages which permit good water flow through the pens. The upper portions of the net cages are supported by and secured to a buoyant surrounding structure such as a full perimeter floating collar assembly which supports an interconnecting decking structure such as walkways. The walkways, which generally include stanchions for supporting hand railings and net attachments, are used by fish farmers in the course of manual or automatic fish feeding, fish inspection, and storage of supplies, as well as for access to nets in the course of maintenance tasks. Flotation structures having spaced-apart flotation units expose the netting to damage from driftwood or other floating debris. Those structures having metal, styrofoam or wooden component parts are subject to damage from attack by salt water, petrochemical pollution or sea worms. When subjected to wave action, such flotation structures are frequently noisy and subject to excessive wear and reflex movements, all of which are disturbing to the fish and limit the life of the assembly.
Full perimeter floating tubular collars made from single or double floating plastic pipes are becoming increasingly popular, particularly in environments prone to strong winds and significant wave action. Such collars provide substantial floating capacity while their position directly on the water surface offers a minimal profile to wind. The low profile also minimizes reflex movements due to wave action, resulting in a more gentle udulating motion transmitted to the net which, in turn, is less disturbing to the fish and contributes to increased yields. Such collars also act as a trash and log barrier substantially blocking debris from contact with the netting.
In general, tubular support collars for marine applications are assembled from tubular segments filled with flotation material such as polystyrene. The abutting ends of adjoining segments are typically joined by an oversleeve which is welded to one end of a tubular segment and joined by a pin or similar connector to the adjacent tubular segment. Such connections, however, are not waterproof and are subject to infiltration by water which may eventually deteriorate the low density flotation material and reduce the collar buoyancy.
A more serious problem is that the oversleeve must be large enough to readily slip over the tubular segments during assembly of the flotation collar--often in situ under adverse construction conditions. The tolerances required for assembly purposes creates looseness or "slop" in the joint connection. Wave action, working continuously on the loose joint slop may eventually cause the connection to weaken and fail. Collar segments of varying configurations are assembled end-to-end so as to construct a collar assembly of desired size and shape to suit a particular application. The assemblies described above, however, either require the transfer of fish during their growth to progressively larger pens or, in the alternative, require the periodic disconnection and reassembly of the collar assembly to achieve a required size. Such repeated on-site modifications are time consuming, costly and can result in accidental loss of fish.
Finally, aquaculture flotation collar assemblies generally employ double, parallel tubular segments joined along their facing inner perimeters by a plurality of separators which serve as a support for planking or other walkway material. Such a walkway configuration is not only potentially unsafe for users because it is subject to "swamping" from even relatively minimal wave action, but is also subject to damage and fouling from marine contamination thereby requiring more frequent cleaning, repair, and/or replacement.
A need exists for a modular flotation support collar assembly which is sealed from infiltration of water during use and in the course of in-water assembly, and for a method of joining component parts of such an assembly together with a connecting joint that will resist working apart due to wave action. A need also exists for such an assembly having walkways positioned above the reach of normally encountered wave action and for a modular flotation support collar assembly which permits pen enlargement during in-water use so as to accommodate fish growth without the need for costly and time consuming modifications to the collar perimeter.